Processing torch having a separably assembled torch base and torch head

ABSTRACT

A processing torch having a separably assembled torch base and torch head includes a first ring member rotatably provided on an outer periphery of one of the torch base and the torch head, and a second ring member fixed on the other one of the torch base and the torch head. An engaging projection is provided on one of the first and second ring members, and an inclined track provided on the other of the first and second ring members for engaging with the engaging projection. In addition, an elastic biasing member is provided for increasing an engaging force between the inclined track and the engaging projection so as to sealingly engage the inclined track and the engaging projection. Connection and disconnection between the torch base and the torch head are performed by rotation of at least one of the first and second ring members.

TECHNICAL FIELD

The present invention relates to a processing torch, such as a plasmatorch, in which a torch body can be assembled separably into a torchbase and a torch head.

BACKGROUND ART

A first conventional fixing means (1) for a connecting portion betweenthe torch base and the torch head is a cap nut type threading structureas disclosed in the Japanese Examined Patent Publication No. Heisei3-27309 and Japanese Examined Patent Publication No. Heisei 5-5589.

A second conventional fixing means (2) is the combination of a clawshaped projecting portion which is provided on one of the torch head andthe torch base and inclined projection which is provided on the other ofthe torch head and the torch base so as to establish thread-typeengagement between the torch head and the torch body by relativerotation, as disclosed in Japanese Examined Patent Publication No. Showa63-13793 and Japanese Unexamined Utility Model Publication No. Heisei3-14076.

A third conventional fixing means (3) is a quick joint system, in whicha steel ball is engaged with a recessed portion, as disclosed inJapanese Examined Utility Model Publication No. Showa 5-19186 andJapanese Unexamined Patent Publication No. Heisei 6-198450.

In the processing torch, expendables, such as an electrode, a nozzle andso forth, are included. For reducing the burden of exchanging, and forshortening of exchanging time, a separable assembling type processingtorch has been considered, whereby when the torch head is released fromthe torch base, a water passage is separated at the connecting portionto cause leakage of the water to make the connecting surface wet.

Upon separation of the torch head and the torch base, a water pump isstopped. The water may not flow in the connecting portion. Therefore, itis considered that leakage of water may not be caused. However, waterremains in the path from the pump and the torch, and this remainingwater may flow out from the connecting portion upon separation, to causewater leakage. Then, upon arc firing, electric leakage or insulationfailure can be caused.

Therefore, in order to prevent the water leakage, it becomes necessaryto have a water stop mechanism upon separation of the torch. The onedisclosed in Japanese Unexamined Patent Publication No. Heisei 6-198450and Japanese Unexamined Patent Publication No. Showa 62-275580, while adifference of water passage and gas passage is present, closes thepassage upon separation, and upon assembling, the passage is opened bythe projection.

The above prior art (1) is reliable as a secure fixing means, but thecap nut has to be rotated for several turns upon connection andseparation, resulting in a long period for connection and separation.Certain measure may be taken by making the thread pitch of the cap nutgreater to reduce rotation angle for threading. However, when the pitchis made greater, greater rotation torque becomes necessary to exert thesame threading force. Therefore, it is not expedient to provide thegreater pitch for significant load upon exchanging of the torch head. Onthe other hand, in case of the cap nut, it is easy to cause crushing ofthe thread. Thus, in consideration of automatic exchange by a machine,special measure has to be taken so as not to crush the thread.

In the above-mentioned prior art (2), the claw shaped projection ishooked to the projection with an inclination to generate an axial forceby the inclination without using threading. In this system, sufficienttightening which can not be established or engagement which can beeasily loosened results when an error occurs in the relative position ofthe projections in the axial direction. Therefore, in order to becertainly fixed, adjustment of both projections becomes necessary. Also,since a plurality of torch heads are connected as exchanged to one torchbase, adjustment of the relative position of the projections becomesnecessary for every torch head, resulting in a long period forperforming an exchanging operation.

Furthermore, another problem of the foregoing prior art (2) is that, forthe structure to establish slip contact between the projections withrespect to each other, if the contact surface is worn, the relativeposition of the projections may diverge to make the axial biasing forcesmaller to require re-adjustment of the relative position between theprojections. On the other hand, the gradient of the spiral projection isdetermined by an angle depending upon a required axial motion magnitudeand rotatable angle. A 2 to 5 mm axial motion magnitude from abutment ofan O-ring at the inserting portion should be required. When the engagingportions of respective projections are formed at two portions on thecircumference, the rotation angle becomes 180° and the gradient isdetermined based thereon. However, since the thus determined gradient isrelatively large, a rather large rotational torque becomes necessary forobtaining sufficient axial force making it difficult to connect andseparate manually.

Furthermore, in the above-mentioned prior art (3), connection can becompleted by inserting the torch head into the torch base in the axialdirection and thus is advantageous to be quite easily connected anddisconnected. However, this holds a drawback because a small pushingforce in the axial direction at the connecting portion to causes a playin the axial direction. Therefore, a complicated structure becomesnecessary for generating a sufficient pressure in the axial direction tomake the connecting portion large. In the construction disclosed inJapanese Examined Utility Model Publication No. Heisei 5-19186, axialdepression force is generated by means of a spring. However, since thedepression force becomes the force necessary upon insertion, when thespring force is set to permit manual loading, sufficient axialdepression force cannot be obtained.

The reason why sufficient axial depression force is necessary at theconnecting portion is that the torch head can be offset from the torchbase due to vibration or so forth due to movement thereof to causeoffset of the tip position of the torch to cause an adverse influence oncutting performance. Also, when an O-ring is present on the connectingsurface, further depression force becomes necessary to make sealingeffective. In the case where the connecting structure requires surfacepressure for flowing sufficient plasma current, further axial depressionforce becomes necessary.

The seal surface of the inserting portion having the water passage andthe gas passage of the torch base and the torch head in the processingtorch, is generally straight. With respect to the O-ring provided atthis portion, axial force becomes necessary from the beginning ofinsertion to make connection and disconnection difficult. The structurewhere the seal surface of the inserting portion is formed into a taperedshape has been disclosed in Japanese Examined Patent Publication No.Heisei 3-27309. In practice, an O-ring for sealing becomes necessary. Atthis time, in order to form coaxial passages, the inner diameter of theO-ring becomes large to make a total contact area of the O-ring large.Accordingly, a large axial force becomes necessary to crush the O-ringfor establishing a seal On the other hand, concerning water leakage uponseparation in the connecting portion of the water passage, this can beprevented by applying the opening and closing valve disclosed inJapanese Unexamined Patent Publication No. Heisei 6-198450 and JapaneseUnexamined Patent Publication No. Showa 62-275580. In such construction,when the connecting portion is disconnected during operation of thepump, the valve is closed to build-up a dangerously high pressure withinthe piping (connecting portion) between the pump and the valve.Furthermore, an impulsive load may act on the pump to cause failure. Onthe other hand, in the case of the separable type torch as disclosed inJapanese Unexamined Patent Publication No. Heisei 6-198450, when anozzle at the tip end, an electrode or so forth is to be exchanged inthe condition where the connecting portion is connected, water leakageshould be caused since the valve is held open.

In view of the problems set forth above, it is a first object of thepresent invention to provide a processing torch which can be easily beseparated from and connected to a separably assembling type torch mainbody manually, which can effectively seal a connecting portion of awater passage or a gas passage in the torch main body, and which canprevent water leakage even upon exchanging of expendables or uponseparation.

On the other hand, in the case of the conventional separable type torch,when the torch head is separated with respect to the torch base, thewater passage is separated at the connecting portion. Therefore, aconnecting portion of the water passage is provided with a water stopvalve for preventing the water leakage which can automatically close thewater passage in response to separation of the torch head.

In the particular structure disclosed in Japanese Unexamined PatentPublication No. Showa 60-9586, water stop valves for water passages ofan in-flow side and an out-flow side are arranged at positions distancedin a direction perpendicular to an axis of the torch base. Respectivewater stop valves are opened by connection of the torch head and closedin response to separation.

On the other hand, in the case of this kind of separable type torch, acurrent to the electrode of the torch head flows to the electrode fromthe torch base to the torch head. At this time, the foregoing currentmay flow even to the water stop portion provided in the water passage,when these structural parts are electrically conductive bodies.

However, in the case of the water stop structure of the water passage asdisclosed in Japanese Unexamined Patent Publication No. 60-9586, itbecomes necessary to separately provide two water stop valves of thesame structure, separately. Therefore, this prevents the connectingportion from being constructed in a compact manner, and requires agreater number of processing process making it difficult to lower thecost thereof.

On the other hand, the passages at the in-flow side and the out-flowside mutually communicated with via respective water stop valves areprovided separately at the base end side of the torch head to make theprocessing at this portion troublesome.

Also, when the electrode current flows through the water stop valve inthe water passage, particularly, when the current flows through thespring for stopping water biasing the valve body of the water stop valvein the closing direction, the spring for stopping water may be melteddown since the current is a large current and the wire forming thespring for stopping water has a small diameter, thereby spoiling thewater stop function.

In view of the problems set forth above, a second object of the presentinvention is to provide a processing torch which can simplify aconstruction of a water stop valve for preventing water leakage at theconnecting portion in respective water passages for inflow and outflow,which permits the connecting portion to be compact, which permitssignificant reduction of the processing cost, which can prevent theelectrode current from flowing through a spring for stopping water inrespective water stop valves, and which and can prevent the spring frommelting down.

DISCLOSURE OF THE INVENTION

In order to accomplish the foregoing first object, according to thefirst aspect of the present invention, there is provided a processingtorch, in which a torch body is separably assembled with a torch baseand a torch head, characterized in that:

a ring member is rotatably provided on the outer periphery of one of thetorch base and the torch head, and another ring member is fixed on theother, an engaging projection is provided on one of both ring membersand a inclined track is provided on the other to engage the engagingprojection with the inclined track, an elastic member biasing forincreasing engaging force between the inclined track and the engagingprojection, and wherein connection and disconnection between the torchbase and the torch head are performed by rotation of the ring member.

With the construction set forth above, since the torch base and thetorch head of the processing torch can be assembled and separated bybayonet coupling structure. Therefore, both are easily connected anddisconnected manually. Also, while connected, since biasing force by thespring is constantly act on the connecting portion, the connectingportion can constantly maintain the tight connecting condition, and maynot be loosened even by vibration or impact.

On the other hand, the connecting member, such as the ring member or soforth is supported by the spring member, so that if a slight dimensionalerror is present between the engaging groove and the engagingprojection, it can be absorbed by flexure of the spring member to permitthe connection of the torch base and the torch head.

On the other hand, in the foregoing construction, it is preferred thatan inclination of the inclined track is steep in the vicinity of aninlet portion and is gentle in other portion. Thus, in the initial stageof the coupling, an axial movement is quickly caused in the large pitch,and subsequently, an axial movement is cause in small pitch so that thecoupling with large coupling force can be established with small force.As a result, the coupling can be done quickly and easily.

On the other hand, in the construction set forth above, it is desirablethat the inclined track is provided with a return preventing means forno-returning of the engaging projection.

Also, in the construction set forth above, it is desirable that bothrings mutually engage at the portions outside of the engaging portion ofthe inclined track and the engaging projection, and that the engagingportion has a sealing structure.

Also, in the construction set forth above, connecting members of torchbase side and torch head side of a medium passage may be formed intotapered-shaped configuration to tightly engage with each other, and asealing member is disposed between mating surfaces of the connectingmembers. Thus, the connecting in the medium passage at the connectingportion between the torch base and the torch head can be establishedwithout any leakage.

In the construction set forth above, it is desirable that a no-returnvalve is provided in a passage on the torch base side of a mediumpassage. Thus, as long as the supply of the medium is stopped, themedium in the medium circuit is enclosed in the torch base side. As aresult, upon the separation at the connecting portion, or the exchangingof expendables in the connected condition, the leakage of medium can beavoided.

Furthermore, it is desirable in the foregoing construction that ano-return valve is provided in the vicinity of a connecting portion.

In order to accomplish the second object of the present invention,according to the second aspect of the invention, there is provided aprocessing torch, in which a torch body is separably assembled with atorch base and a torch head, characterized in that:

a plurality of medium passages are provided in one connecting portionbetween the torch base and the torch head.

With the construction set forth above, the medium passage for inflow andoutflow, for example provided in the torch base and the torch head, canbe aggregately provided at one portion to make the connecting portionthinner and compact.

In the construction set forth above, it is preferable that medium stopvalves are provided in respective ones of a plurality of mediumpassages, and that there are provided opening and closing members foropening and closing the medium stop valves substantially at the sametiming, upon separating and assembling of the torch base and the torchhead.

In the foregoing construction, it is desirable that the plurality ofmedium passages are provided coaxially or in parallel.

Furthermore, in the foregoing construction, it is desirable that atleast one of a member forming the medium stop valve and the opening andclosing member for opening and closing the medium stop valve isnon-conductive. Thus, a large current for plasma will never flow throughthe spring employed in the medium stop valve, and melting down of thespring which can be caused by the flow of large current is prevented.

On the other hand, according to the third aspect of the presentinvention, there is provided a processing torch, in which a torch bodyis separably assembled with a torch base and a torch head, characterizedin that:

a connecting portion between the torch base and the torch head isexchangeable.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings of thepreferred embodiments of the present invention, which, however, shouldnot be taken to be limitative to the present invention, but are forexplanation and understanding only.

In the drawings:

FIG. 1 is a exploded perspective view of the first embodiment of aprocessing torch according to the present invention;

FIG. 2 is an explanatory illustration showing a relationship between ashape of an engaging groove in the first embodiment and a generatedaxial force versus a rotational angle upon bayonet coupling, in which anengaging projection is engaged with the engaging groove;

FIGS. 3A, 3B and 3C are general illustrations of modification of theforegoing engaging grooves, respectively.

FIGS. 4A and 4B are sections showing another example of a inclined trackfor bayonet coupling, and engaging condition of the shown example of theinclined track and the engaging projection;

FIGS. 5A and 5B are sections showing a further example of a inclinedtrack for bayonet coupling, and an engaging condition of the shownexample of the inclined track and the engaging projection;

FIG. 6A is a section of another example of a ring member at a torch baseside having a inclined track for bayonet coupling;

FIG. 6B is a section of a further example of a ring member at a torchbase side having a inclined track for bayonet coupling;

FIG. 6C is a perspective view of a still further example of an engagingprojection;

FIG. 6D is a perspective view of a still further example of the inclinedtrack;

FIG. 7 is a section showing an example of engaging portion of both ringmembers at the torch base side and a torch head side;

FIG. 8 is a section showing assembling condition of the torch base andthe torch head of the second embodiment of a processing torch accordingto the invention;

FIG. 9 is a section showing a condition where the second embodiment isrotated over 90°;

FIG. 10 is a section showing a major part of the condition where thetorch base and the torch head of the second embodiment are separated;

FIG. 11 is a section showing another example of the water stop valveportion; and

FIG. 12 is a section of another example of a pipe having both inflow andoutflow passages.

BEST MODE FOR IMPLEMENTING THE PRESENT INVENTION

The preferred embodiment of the processing torch of the presentinvention will be discussed hereinafter with reference to theaccompanying drawings.

The first embodiment of the processing torch according to the inventionwill be discussed with reference to FIGS. 1 and 2.

In FIG. 1, 1 denotes a processing torch, in which a torch base 2 and atorch head 3 can be assembled separably. On a tip end of the torch head3, an electrode 4, a nozzle 5, a shield cap 6 and so forth are providedsimilarly to the tip end structure of the normal processing torch. Then,on the inside of the electrode 4 and the outside of the nozzle 5,cooling water passages 4a and 5a are provided. By cooling water flowingtherethrough, the electrode 4 and the nozzle 5 are cooled. It should benoted that the members outside of the nozzle 5 are electricallyinsulated by an insulation cylinder 7.

Also, on the base end portion of the torch head 3, an inflow valve sideprojecting portion 8 and a return valve side projecting portion 9communicated with the cooling water passages 4a and 5a, respectively,are projected. These both projecting portions 8 and 9 are formed intotapered shaped configuration and fitted with O-rings 8a and 9a on theouter periphery. On the other hand, on the base end of a core portion ofthe torch head 3, a head side connecting surface 11 electricallyconnected to the torch base 2 side is provided.

It should be noted that, while it is not illustrated on the drawings, onthe torch head 3, respective supply passages for a working medium gas tobe ejected toward the tip end portion of the electrode 5 and an assistgas to be ejected between the nozzle 5 and the nozzle cap 6 are extendedfrom the tip end to the base end. These passages are connected to thepassages on the side of the torch base 2 by connecting the torch head 3to the torch base 2. Constructions of the connecting portions of thesegas passages are the same as that of the connecting portion of theforegoing cooling water passages.

On the base end of the torch head 3, a cylindrical member 12 is fittedvia an insulation member 12a. By inserting an inner cylindrical portion13 into the torch base 2 into the cylindrical member 12, the torch head3 and the torch base 2 are connected. On the bottom surface of the innercylindrical portion 13 of the torch base 2, an inflow valve siderecessed portion 14a and a return valve side recessed portion 15a formedinto reverse tapered shape for tightly engaging with the inflow sideprojecting portion 8 and the return side projecting portion 9 of thetorch head 3, respectively, are provided. The inflow passage 14 and thereturn passage 15 are communicated with the recessed portions 14a and15a, respectively. Also, on the bottom surface of the inner cylindricalportion 13, a base side connecting surface 16 contacting with a headside connecting surface 11 of the torch head 3 is provided.

On one of the outer peripheral surface of the cylindrical member 12 ofthe torch head 3 and the inner peripheral surface of the innercylindrical portion 13 of the torch base 2, a positioning groove 17 isprovided, and a positioning pin 18 engaging with the positioning grooveis provided on the other. By engaging the cylindrical member 12 with theinner cylindrical portion 13 with engaging the position pin and thepositioning groove, the connection can be established without causing aphase error of the cooling water passage and the not shown gas passage.

On the bottom portion of the return side recessed portion 15a of thetorch base 2, a no-return valve 21 constituted of a ball 19, a spring 20and a valve seat 21a, is provided. On the other hand, in the inflowpassage 14 of the torch base 2, a no-return valve 24 constituted of aball 22, a spring 23 and a valve seat 24a, is provided. It should benoted that the no-return valves 21 and 24 are provided in the vicinityof the recessed portions 14a and 15a, respectively.

On the end portion of the torch base 2, a ring member 2a is fixed bymeans of a bolt 2b. On the outer periphery of the ring member 2a, aplurality of engaging grooves 25 to be inclined tracks for bayonetcoupling are formed to form a part of spiral. For instance, two engaginggrooves are provided with angular offset of 180° in the circumferentialdirection.

On the other hand, on the out side of the end of the torch head 3, aring member 26 is engaged in a direction parallel to the axis via a leafspring 27 having flexibility. On the inner surface of the ring member26, an engaging projection 28 for engaging with respective engaginggrooves 25 are provided. It should be noted that the engaging projection28 is supported on the ring member 26 in a condition rotatable in thecircumferential direction via a bearing 29.

The engaging groove 25 is constructed with an inlet portion 25a, towhich the engaging projection 28 is engaged in the axial direction, ainclined portion 25b, on which the engaging projection 28 engagesslidingly to move in a direction forming a part of the spiral, and ahorizontal portion 25c at the terminating end. Then, the inclinedportion has a steep inclination at the portion close to the inletportion 25a and a gentle inclination at the portion close to theterminating end portion. The inclination of the inclined portion 25b isvaried in two stages.

On the other hand, the leaf spring 27 mounting the ring member 26 to thetorch head 3 is divided into a plurality of pieces in thecircumferential direction. Each of the divided pieces of the leaf spring27 is rotatable about the torch head 3 and movable in the axialdirection, and is engaged with a flange portion 12b formed on the outerperiphery of the cylindrical member 12 so that, at least, they may notloose away from the torch head 3. To these leaf springs 27, the ringmember 26 is fixed.

On the other hand, to a flange portion 30 of the torch base 2 and thering member 26 of the torch head 3 side, positioning marking 31a and 31brespectively corresponding to the inlet portion 25a of the engaginggroove 25 and the engaging projection 28 are respectively provided inrecessed form so as to be seen externally.

Furthermore, on the end surface portion of the ring member 26, an O-ring32 contacting with the flange portion 30 on the torch base 2 side isengaged.

The engagement relationship between the engaging projection 28 projectedon the ring member 26 and the engaging groove 25 of the torch base sideis that the connecting surfaces of the torch base 2 and the torch head 3are abut with each other at the stage where the engaging projection 28is engaged with the horizontal portion 25c of the engaging groove 25, toflex the leaf spring 27 toward the torch base 2 side, and the engagingprojection 28 is biased toward the horizontal portion 25c of theengaging groove 25 by spring to engage thereto. At this condition, thetorch base 2 and the torch head 3 are tightly engaged.

Next, in the foregoing first embodiment, the procedure for connectingand disconnecting the torch head 3 to and from the torch base 2 will bediscussed hereinafter.

To the inner cylindrical portion 13 of the torch base 2, the cylindricalportion 12 of the torch head 2 is engaged with engaging the positioningpin 18 to the positioning groove 17. In conjunction therewith, theengaging projection of the ring member 26 is engaged from the inletportion 25a of the engaging groove 25 on the torch base 2 side. At thiscondition, the inflow valve side projecting portion 8 and the returnvalve side projection 9 on the torch head 3 side are respectivelyinserted into the inflow valve side recessed portion 14a and the returnvalve side recessed portion 15a. The O-rings 8a and 9a therebetween aresituated in the condition to lightly contact with the recessed portions14a and 15a. Thus, inserting operation can be performed with a smallforce. And, at this time, the ring member 26 is positioned by using thepositioning markings 31a and 31b.

Next, the ring member 26 is rotated (angular displacement over 90° inright direction in the shown embodiment). By this, the engagingprojection 28 moved in the axial direction in conjunction with movementalong the engaging groove 25 to establish bayonet coupling therebetween.

At this time, since the steep inclination is provided at the portion ofthe inclined portion 25b close to the inlet portion 25a of the engaginggroove 25, by the initial rotation of the ring member 26, the engagingprojection 28 is moved in the axial direction in large magnitudetogether with the torch head 3. At this time, since it is only requireda force in the axial direction for causing elastic deformation of theO-rings 8a and 9a, not so large rotational force is required despite ofthe fact that the inclination is steep. Subsequently, the engagingprojection 28 engages with the portion having gentle inclination of theinclined portion 25b to apply large axial force with small rotationalforce. Thus, the torch head 3 can be firmly depressed in the axialdirection onto the torch base 2. Then, the engaging projection 28engages the horizontal portion 25c at the terminating end of theengaging groove 25 to complete connecting operation. Then, the ringmember 26 is engaged and fixed to the torch base 2 side.

At this time, a relationship between the rotational angle of the ringmember 26 and the axial force generated is as shown in FIG. 2. In thisembodiment, the rotational angle of the ring member 26 is set at 90°.

And, at this time, since the ring member 26 is resiliently supported onthe leaf spring 27, the torch head 3 is constantly biased in theconnecting direction by the biasing force generated by flexure of theleaf spring 27. And also, in this connecting condition, the end surfaceportion of the ring member 26 is contacted with the flange portion 30 ofthe torch base 2 under pressure to establish a seal. Therefore, theconnecting portion can be protected from the powder dust. Besides, adust seal can be used in place of O-ring to protect from the powderdust.

Upon connection of the torch base 2 and the torch head 3, the inflowside of the cooling water passage is communicated by engagement betweenthe inflow valve side projecting portion 8 and the inflow valve siderecessed portion 14a, and the return side is communicated by engagementof the return valve side projecting portion 9 and the return valve siderecessed portion 15a.

Then, the cooling water flows with opening the no-return valve 24 in theinflow passage under pressure to flow thereinto, and the water in thereturn side opens the no-return valve 21 in the return passage underpressure to permit flow out.

The separation of the torch head 3 from the torch base 2 is performedthrough the procedure reverse to the foregoing.

Upon the separation, since the supply of the cooling water is stopped,the water in the inflow passage for the cooling water is sealed byno-return valve 24. Also, the water in the return passage is sealed bythe no-return valve 21. Thus, the cooling water will never cause aleakage of the cooling water. At this time, water present between theboth no-return valves 21, 24 to the valve side recessed portions 14a and15a may flows out. Since positions of both no-return valves 21 and 24are close to the valve side recessed portions 14a and 15a, the wateramount can be small and will not cause a significant problem.

In the first embodiment, the engaging groove 25 as the inclined trackfor bayonet coupling is varied the inclination in stepwise fashion.However, as shown in FIG. 3A, it is possible to form the engaging groove25 inclined in arc-shaped stepless fashion. On the other hand, as shownin FIG. 3B, the terminal end portion of the engaging groove 25 isprovided with the reverse inclination. At this time, the magnitude ofthe reverse inclination is quite small, the loosening of coupling by thereverse inclination is absorbed by the resilient deformation of the leafspring 27. On the other hand, as shown in FIG. 3C, it is possible toprevent the coupling from loosening by providing a plurality of recessedportions in the engaging groove 25, to which the engaging projection 28is engaged.

While the inclined engaging groove 25 is employed in the inclined trackof the bayonet coupling portion in the foregoing first embodiment, itmay be possible to employ the projecting track 33 as shown in FIG. 4Aand a ball shaped (or plunger form) engaging member 34 provided on thering member 26a is rotatingly contact with the upper surface of theprojecting track 33 as shown in FIG. 4B.

On the other hand, as shown in FIG. 5A, an engaging groove 25e ofV-shaped cross-section are provided. By engaging the ball-shapedengaging member 25 to the engaging groove, engagement is established asshown in FIG. 5B.

On the other hand, in the foregoing first embodiment, a construction, inwhich the ring member 2a of the torch base 2 side, provided the engaginggroove 25 is fixed on the torch base 2 by the bolt 2b, and the ringmember 26 of the torch head 3 side supporting the engaging projection 28engaging thereto, is supported by the leaf spring 27 having flexibilityin the axial direction. Conversely, as shown in FIG. 6A, the ring member2a on the side of the torch base 2 may resiliently supported by the leafspring 36 to fix the ring member 26 on the torch head 3 side on thetorch head 3, may be employed.

It is also possible to fix both ring members 2a and 26 on respective ofthe torch base 2 and the torch head 3, and support a bearing base 37supporting the engaging projection 28 in axially slidable fashion bybiasing them to the ring member 26 of the torch head 3 side with theelastic member, such as the spring 38, rubber or so forth on both sidesin the axial direction, as shown in FIG. 6B. On the other hand, as shownin FIG. 6C, it is possible to bond the elastic member 39, such as rubberor so forth, on the outer periphery of the engaging projection 28 toapply a biasing force in the axial direction to the bayonet couplingportion by the elastic force of the elastic member 39.

On the other hand, as shown in FIG. 6D, it is possible to bond theelastic member 41 on the upper surface of the inclined track 40, tocontact with the engaging projection 28 to apply a biasing force in theaxial direction to the bayonet coupling portion by the elastic force ofthe elastic member 41. On the other hand, as shown in FIG. 1, similareffect to the foregoing may be obtained by fitting the foregoing elasticmember 41 on the inner surface of the engaging groove 25 contacting withthe engaging projection 28.

Also, concerning the seal of the connecting portion between the torchbase 2 and the torch head 3, as shown in FIG. 7, the top portion of thering member 26 on the torch head 3 side engages with the groove of thering member 2a of the torch base 2 side in liquid tight fashion to forma sealing structure of the connecting portion without employing theO-ring.

On the other hand, in the first embodiment, the outside constructionalmembers of the torch base 2 and the torch head 3 are insulated from theinside conductive members by constructing them with an insulative memberor so forth, or, in the alternative, to interpose the insulative memberbetween both side members.

By the foregoing first embodiment, the separable assembling of the torchbase 2 and the torch head 3 of the processing torch 1 is realized by thebayonet coupling, and thus both of them can be easily connected anddisconnected manually. Then, in the connection, the biasing force in theaxial direction by the spring constantly acted to the connectingportion. Therefore, the connecting portion can constantly maintain thetight connecting condition and may not be loosen by vibration or impact.

On the other hand, since the connecting member, such as the ring member26 or so forth is supported by a spring member, even when a slightdimensional error is present in the engaging portion by the engaginggroove and the engaging projection, those are absorbed by flexure of thespring member to connect the torch base 2 and the torch head 3.

On the other hand, by providing the steep inclination at the portion inthe vicinity of the inlet portion and the gentle inclination at theremaining portion in the inclined track of the bayonet coupling to varythe inclination of the inclined track two or more stages. Therefore, atthe initial stage of the coupling, large pitch axial movement is causedto cause swift axial movement, and subsequently an axial movement in thesmall pitch is caused so that the coupling with large coupling force canbe established with small force. As a result, the coupling can beestablished quickly and easily.

Furthermore, since the members forming the connecting portions of theinflow passage, the return passage and further the not shown gas passagefrom the torch base 2 to the torch head 3, between the torch base 2 andthe torch head 3, are formed into tapered shape for tightly engagingwith each other, and the O-ring is disposed between the mating surfacesof the members, leakages in the both cooling water passages and the gaspassage will never caused at the connecting portion between the torchbase 2 and the torch head 3.

On the other hand, since the no-return valves are disposed in both ofthe cooling water inflow and return passages in the torch base 2, whenthe supply of the cooling water is stopped, the water in the coolingwater circuit is enclosed on the torch head 2 side. As a result, whenthe coupling portion is separated or exchanging of the expendables onthe head side in the connected condition is executed, the water leakagecan be avoided.

Next, discussion will be given for the second embodiment of theprocessing torch according to the present invention with reference toFIGS. 8 to 10.

In FIG. 8, 101 denotes a processing torch constructed for separablyassembling a torch base 102 and a torch head 103. These torch base 102and the torch head 103 can be connected and disconnected by a connectingdevice 104 of the bayonet structure similarly to the first embodiment.

Namely, from the inner surface of a bayonet type ring member 120supported on the torch head 103 via a leaf spring 127, two pins 126, 126are projected. On the outer peripheral surface of a ring member 136fixed to the torch base 102, inclined grooves 125, 125 forming a part ofspiral are provided. When the pins 126, 126 are engaged with thesegrooves 125, 125 and the torch head 103 is relatively rotated withrespect to the torch base 102, both members are connected by selfholding force of the pin 126 to the groove 125 and flexure of the leafspring 127. By performing reverse operation, both members are separated.

On the tip end portion of the torch head 103, similarly to the structureof the tip end portion of the normal processing torch, an electrode 105,a nozzle 106, a shielding cap 107 or so forth are provided. Then, on theinside of the electrode 105 and the outside of the nozzle 106, coolingwater passages 108a and 108b are provided, respectively so that theelectrode 105, the nozzle 106 and so forth are cooled by the coolingwater flowing therethrough. It should be noted that the members outsideof the nozzle 106 are electrically insulated by an insulation cylinder105a with respect to the electrode 105.

The connecting condition of the torch base 102 and the torch head 103 bythe connecting device 104 are connected in mutually contacting conditionof the end surfaces of the base body 109 of the torch base 102 side andthe head body 110 of the torch head 103 side.

Then, from the head body 110, a water passage connecting cylinder 111 isprojected. In the axial portion of the water passage connecting cylinder111, a inflow pipe 112 opened at the tip end thereof is provided. On theother hand, on the outside of the inflow pipe 112, an annular outflowpassage 114 communicated with a through hole 113 opening to the outerperipheral surface of the water passage connecting cylinder 111 isprovided coaxially with the inflow pipe 112.

The lower end of the inflow pipe 112 opens to an annular cooling waterpassage 108a in the electrode 105. The cooling passage 108a is providedcoaxially on the outside of the inflow pipe 112 to communicate with theoutflow passage 114 of the head body 110 via the cooling water passage108b located outside of the nozzle 106.

On tip end side of the through hole 113 on the outer peripheral surfaceof the tip end portion of the water passage connecting cylinder 111, anupwardly directed step portion 111a is provided. On the other hand, onthe tip end of the water passage connecting cylinder 111, a radiallyextending water flow groove 115 is provided.

On the base body 109 of the torch base 102, a hole 116 to which thewater passage connecting cylinder 111 is engaged is provided. Within theopening end portion of the hole 116, a bushing 117 to tightly engagewith the water passage connecting cylinder 111 is engaged. Also, on thewall surface on the bottom side of the bushing 117, an outflow opening118 is opened. On the bottom side of the bushing 117, an outflow valve119 vertically slidable from a position to contact the lower end thereofwith the end portion of the bushing 117 to close the outflow opening 118to the position to open the outflow opening 118, is engaged. The outflowvalve 119 is biased in the direction to close the outflow opening 118 bymeans of a spring 120. By the outflow valve 119, the spring 120 and thebushing 117, a water stop valve A on the outflow passage side is formed.

The inner diameter of the outflow valve 119 is smaller than that of thebushing 117 so that the step portion 111a of the water passageconnecting cylinder 111 contacts with the lower end thereof to push theoutflow valve 119 in the opening direction of the outflow opening 118against the spring 120.

On the inside of the outflow valve 119, an upwardly tapered valve seatsurface 119a is provided. On the valve seat surface 119a, an inflowvalve 121 which is slidably engaged in the most backside of the hole 116of the base body 109 and biased in the closing direction by means of aspring 122 is contacted. With the inflow valve 121, the spring 122 andthe valve seat surface 119a, the inflow side water stop valve B isformed. It should be noted that the inflow valve 121 is formed with aslit 121a for improving an inflow efficiency of the water. Then, in thebase body 109, an inflow pipe 123 communicated with the most backside ofthe hole 116 is connected.

The length from the step portion 111a to the tip end of the waterpassage connecting cylinder 111 is set in a length to push the inflowvalve 121 to be higher than the outflow valve 119 by the tip end in thecondition where the outflow valve 119 is pushed up by the steppedportion 111a. Therefore, in the condition where the torch head 103 isconnected to the torch base, both valves 119 and 121 are opened by thewater passage connection cylinder 111.

The outflow valve and the inflow valve 119 and 121 are constructed withnon-conductive material, such as resin, ceramic or so forth. It shouldbe appreciated that the springs 120 and 122 and the water passageconnecting cylinder 111 may be formed of non-conductive material. In thealternative, the member which is formed with the conductive body withcoating of non-conductive material may also be used.

The cooling passage 108a in the electrode 105 in the torch head 103 andthe cooling passage 108b on the outside of the nozzle 106 are connectedby a passage within the torch head 103. Then, a return passage from thecooling passage 108a in the electrode 105 and the return passage to thewater stop valve A side from the cooling passage 108b outside of thenozzle 106 are defined by partitioning the outflow passage 114 formedcoaxially with the inflow pipe 112 and outside thereof, by means of awater stop ring 128.

FIG. 9 is a section of the second embodiment shown in FIG. 8 at aposition rotated over 90°. 129 denotes a working medium gas passage, 130denotes an assist gas passage. These can be connected and disconnectedto the base body 109 side and the head body 110 side by joint members129a and 130a, respectively.

Next, operation of the second embodiment will be discussed hereinafter.

FIG. 10 shows a condition where the torch head 103 is separated from thetorch base 102. At this condition, the outflow valve 119 of the waterstop valve A on the outflow passage side is moved downwardly to contactwith the bush 117 as being biased by the spring 120. Therefore, theoutflow opening 118 provided in the base body 109 is closed to place theoutflow passage in closed position.

On the other hand, the inflow valve 121 of the water stop valve B on theinflow passage side is biased by the spring 122 to contact the inflowvalve 119 of the water stop valve A on the inflow passage side onto thevalve seat surface 119a. Thus, the inflow passage is also placed in theclosed position.

Next, by connecting the torch base 102 and the torch head 103, thecondition shown in FIGS. 8 and 9 is established. Namely, when the waterpassage connecting cylinder 111 provided on the side of the torch head103 is inserted within the hole 109 of the torch base 102, the outflowvalve 119 of the water stop valve A on the outflow passage side ispushed upwardly by the step portion 111a of the water passage connectingcylinder 111 to move upwardly against the spring 120 to open the outflowopening 118 to open the outflow passage.

On the other hand, at substantially the same timing, the tip end of thewater passage connecting cylinder 111 contacts with the inflow valve 121on the inflow passage side to push the latter up against the spring 122to open the inflow passage.

At this condition, the torch base 102 and the torch head 103 are firmlyconnected by the connecting device 104.

Then, upon actuation of the processing torch 101, the cooling water mayflow from the torch base 102 to the torch head 103 through both waterstop valves A and B to cool the temperature elevating portions, such aselectrode 5, the nozzle 6 and so forth.

On the other hand, at this time, the actuation current is input througha connector 131 connected to the upper end portion of the base body 109of the torch base 102, and flows to the electrode 105 from the base body109 to the head body 110.

However, the outflow valve 119 and the inflow valve 121 of both waterstop valves A and B built in the base body 109 are formed ofnon-conductive material, a current may not flow through these.

Accordingly, the current will never flow through respective springs 120and 122 which contact with respective one end of the valves 119 and 121for biasing them in the closing direction.

Therefore, melting down of both springs 120 and 122 due to introductionof large current will never be caused.

In the second embodiment, an example where the outflow valve 119 of thewater stop valve A in the outflow side is formed into a cylindricalshape, has been disclosed. However, the outflow valve 119 is required tohave only a function to open and close the outflow opening 118 providedin the base body 109 according to insertion and releasing of the waterpassage connecting cylinder 111 into and from the hole 116. Therefore,in place of the shown construction, it is possible to construct as shownin FIG. 11, to provide a shutter 119' at a position opposing to theoutflow opening 118 for opening and closing the latter, and to open theshutter 119' by pushing up a projection 132 provided on the inside ofthe shutter 119' by the step portion 111a of the water passageconnecting cylinder 111 against a spring 134 disposed between theprojection 132 and a valve seat member 133 of the inflow valve side. Itshould be appreciated that, in such case, the valve seat member 133having the valve seat surface 119a to contact with the inflow valve 121is held in a condition fixed on the base body 109.

On the other hand, in the second embodiment, the inflow pipe 112 formingthe inflow passage of the cooling water and the outflow passage 114provided in the head body 110 are formed into the double pipe structure.However, for the inflow passage and the outflow passage, a pipe 35, inwhich two passages a and b are arranged in parallel may be used, asshown in FIG. 12. On the other hand, while the second embodiment is anexample employing cooling water passage, the present invention is alsoapplicable for the passage of fluid, such as gas or so forth.

As set forth above, by the second embodiment, in the processing torch,the torch body is formed with the torch base 102 and the torch head 103,both members are connected and disconnected by the connecting means, andthe water stop valves for preventing water leakage in the connectingportion of the water flowing passage for inflow and outflow arecoaxially arranged at one portion, in both member. Therefore, thisembodiment can make the connecting portion thin and compact andsignificantly reduce the processing cost.

On the other hand, in the processing torch as set forth above, a largecurrent for plasma actuation will never flow through the spring employedin the water stop valve. Thus, the melting down of the spring due toflowing of the large current can be prevented.

Although the invention has been illustrated and described with respectto exemplary embodiment thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodies within a scope encompassed andequivalents thereof with respect to the feature set out in the appendedclaims.

We claim:
 1. A processing torch having a separably assembled torch baseand torch head, comprising:a first ring member rotatably provided on anouter periphery of one of said torch base and said torch head, and asecond ring member fixed on the other one of said torch base and saidtorch head, an engaging projection provided on one of said first andsecond ring members, and an inclined track provided on the other of saidfirst and second ring members for engaging with said engagingprojection, and an elastic biasing member for increasing an engagingforce between said inclined track and said engaging projection so as tosealingly engage said torch base and said torch head, wherein connectionand disconnection between said torch base and said torch head areperformed by rotation of said first ring member.
 2. A processing torchas set forth in claim 1, wherein an inclination of said inclined trackis steeper in a vicinity of an inlet portion thereof than in otherportions thereof.
 3. A processing torch as set forth in claim 1, whereinsaid inclined track is provided with a return preventing means forpreventing said engaging projection from returning.
 4. A processingtorch as set forth in claim 1, wherein said first and second ringmembers mutually engage each other at portions outside of an engagingportion of said inclined track and said engaging projection, and whereinsaid engaging portion comprises a sealing structure.
 5. A processingtorch as set forth in claim 1, further comprising:connecting membersprovided on both said torch base and said torch head, said connectingmembers being formed into a tapered-shaped configuration to tightlyengage with each other, and a sealing member disposed between matingsurfaces of said connecting members.
 6. A processing torch as set forthin claim 1, further comprising a valve provided in a passage in saidtorch base.
 7. A processing torch as set forth in claim 1, furthercomprising a valve provided in a vicinity of a connecting portionbetween said torch base and said torch head.
 8. A processing torch asset forth in claim 1, further comprising a plurality of medium passagesprovided in a connecting portion between said torch base and said torchhead.
 9. A processing torch as set forth in claim 8, furthercomprising:a plurality of medium stop valves provided in respective onesof said plurality of medium passages, and an opening and closing memberfor opening and closing said medium stop valves substantially at a sametiming upon separating and assembling of said torch base and said torchhead.
 10. A processing torch as set forth in claim 8, wherein saidplurality of medium passages are coaxially arranged.
 11. A processingtorch as set forth in claim 8, wherein said plurality of medium passagesare arranged in parallel.
 12. A processing torch as set forth in claim9, wherein at least one of said medium stop valves and said opening andclosing member is non-conductive.
 13. A processing torch as set forth inclaim 1, wherein a connecting portion provided between said torch baseand said torch head is exchangeable.
 14. A processing torch as set forthin claim 1, wherein said inclined track is inclined in an arc-shaped andstepless manner.
 15. A processing torch as set forth in claim 2, whereinsaid other portions of said inclined track include a plurality ofrecesses.
 16. A processing torch as set forth in claim 1, wherein saidinclined track comprises a protrusion and said engaging projectioncomprises a ball shaped member, and wherein said ball shaped memberrotatingly contacts an upper surface of said protrusion.
 17. Aprocessing torch as set forth in claim 1, wherein said inclined trackcomprises a protrusion and said engaging projection comprises a plungermember, and wherein said plunger member rotatingly contacts an uppersurface of said protrusion.
 18. A processing torch as set forth in claim17, wherein said upper surface of said protrusion is bonded by anelastic member.
 19. A processing torch as set forth in claim 18, whereinsaid plunger member is bonded by an elastic member.
 20. A processingtorch as set forth in claim 1, wherein said inclined track comprises agroove having a V-shaped cross section and said engaging projectioncomprises a ball-shaped member, and wherein said ball-shaped memberengages said groove.